Rotary fan arrangement



Dec. 21, 1965 o. LJUNGSTRM ETAL 3,224,666

ROTARY FAN ARRANGEMENT Filed April 15, 1964 L71]: J z/zzyszz'im EH71: 111-72! imizz izzzzmmazz United States Patent 3,224,666 ROTARY FAN ARRANGEMENT Olle Ljungstriim, Brevik, Lidingo, Ebhe Karl Johan Gunnarsson, Akersberga, and Per ()lof Eriksson, Stockholm, fiweden, assignors to Sve-nska Aeroplan Aktiebolaget, Linkoping, Sweden, a corporation of Sweden Filed Apr. 15, 1964, Ser. No. 360,034 4 Claims. (Cl. 23t)12t)) This invention relates to an arrangement in an axial flow fan operating in a channel such as an axial flow fan operating in the air intake channel of an air cushion vehicle.

Due to resiliency of the fan unit when in operation, the fan will inherently perform swinging movements relative to the channel. In known fan arrangements wherein the fan unit is mounted independently of the channel wall, and particularly where the fan has a flexible shaft suspension, additional swinging movements of substantially greater magnitude will arise on the fan when it is subjected to shaking or impacts. In order to prevent the fan blades from striking the channel wall due to such increased movements of the fan, it is necessary to provide substantially large clearance between the tips of the fan blades or the fan wheel and the wall, which of course involves a reduction of efficiency of the fan.

An object of the invention is to provide, in an axial flow fan as above described, an arrangement by which a uniform and minimum clearance between the fan and a surrounding channel part can be maintained during op eration of the fan, independently of the magnitude of swinging movements which the fan performs relative to the channel due to internal unbalance or external excitation.

A further object of the invention is to provide such a fan arrangement wherein the clearance between the fan and the surrounding channel part can be adjusted so as to make the clearance uniform all around the fan.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the herein disclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIGURE 1 is a view mainly in perspective but with portions cut away, showing the arrangement of an axial flow fan of this invention mounted in the air intake channel of an air cushion vehicle.

FIGURE 2 is an enlarged sectional view showing parts of the arrangement in FIGURE 1.

On the drawing 2 designates an axial flow fan which is arranged in an air intake channel 1 of an air cushion vehicle and comprises a hub 3 and a number of angularly disposed fan blades 4 projecting radially from the hub and having their tips equidistant from the rotation axis of the fan. In the hub there is attached a cantilever fan shaft 5 which, by means of ball bearings 6, is rotatably mounted in a bearing housing 7 supported by and projecting upwardly from a framework 8 within the channel. The fan is driven by a motor 9 in usual manner. To obtain an aerodynamic shape of the air intake to the fan the hub has a spinner 10 applied thereto.

In the inside of the channel wall, designated by ll, there is made an annular recess 12 of U-shaped cross 3,224,666 Patented Dec. 21, 1965 section which recess is positioned in the plane of the fan opposite to the fan blades 4. A slightly resilient ring 13, having concentric substantially cylindrical inner and outer surfaces and made of a comparatively still material such as glass fibre reinforced plastic, is arranged in the recess so as to encircle the fan blades with a slight clearance between its inner surface and their tips.

The ring, being axially narrower than the recess, is supported therein by two annular seal strips 14 of elastic material, such as rubber or the like, one interposed between each end surface of the ring and its opposing surface of the recess, so that the seal strips cooperate with the inner surface of the ring and the wall of the channel to define a substantially smooth and continuous axially extending duct surface. The ring is also resiliently secured to the bottom surface of the recess by means of a number of elastic supports 15 which are spaced at uniform circumferential intervals around the recess, each comprising a pair of rubber blocks 16 attached to anchor plates 17 and 18 which are in turn screw-fastened to the ring and to the bottom of the recess respectively.

While the ring has a sealed and resilient connection to the channel wall it is radially rigidly connected to the bearing housing 7 by means of a number of comparatively thin spokes 19, such as steel wires, that olfer small resistance to air flow in the air intake channel. The connection of the spokes to the bearing housing is provided by means of a retainer ring 20 rigidly attached to the housing close to the hub and which has a number of circumferentially equally spaced lugs 21 wherein the inner ends of the spokes are received. The outer end of each spoke extends through a corresponding hole 22 in the ring, said holes being so positioned as to dispose the spokes as close as possible to the fan blades, and the outer end of each spoke is arranged to be anchored to the ring by an individual tightening means 23.

As more clearly shown in FIGURE 2 each tightening means comprises an L-shaped member 24 engaging the radially outer surface of the ring and one of its end surfaces within the recess. The L-shaped member has a hole 25 which is concentric with but larger than the hole 22 in the ring and which is adapted to receive a sleeve nut 26 with a collar that engages the outer surface of the L- shaped member. Into the sleeve nut 26 there is threaded a screw 27 with a tapered hole 28 wherein a tapered body 29 attached to the end of the spoke is introduced.

Since the ring is arranged in sealed motion permitting relation to the channel wall but is substantially rigidly connected to the fan unit so as to be constrained to move with the latter in swinging movements of varying magnitude to which the fan unit is subjected on account of internal unbalance or external excitation, the clearance or gap, designated by a in FIGURE 2, between the fan blades and the ring can be made small. It will further be seen that by the individual tightening of the spokes the ring can be properly centered in relation to the axis of the fan shaft and tolerances in its circular shape can be adjusted to thereby obtain a uniform minimum clearance around the whole fan. A precisely accurate clearance may further be obtained by providing the inside of the ring with a coating and machining the coating by means of the tips of the fan blades after the ring is tightened in its position. In addition to providing a sealed floating support of the ring the seal strips also provide a damping effect to eliminate or reduce the tendency toward oscillations of the ring and spokes connected thereto, while the elastic supports primarily serve to carry the dead weight of the ring and also to absorb torsion loads in possible large movements of the ring. Instead of the fan blades being free at their outer ends the fan blades can be connected to a surrounding ring and thus form a fan wheel, in which case the same small clearance as mentioned above can be obtained between the ring of the wheel and the ring in the channel wall.

What is claimed as our invention is:

1. In apparatus comprising wall means defining a ductlike channel, a bearing housing coaxially fixed in said channel, a shaft coaxially rotatable in the bearing housing, and a fan in the channel having a hub fixed to said shaft and a plurality of blades projecting substantially radially from the hub with their tips equidistant from the axis of the shaft:

(A) a still? but slightly resilient ring encircling the fan blades with a small clearance between the tips of the blades and the ring;

(B) means supporting the ring on said wall means, at

the radially inner surface thereof, said means providing for radial motion of the ring relative to the wall means and providing a seal between the ring and the wall means;

(C) a plurality of substantially radially extending spokes, each having its opposite ends connected respectively to the bearing housing and to the ring, said spokes being disposed close to the plane of the blades; and

(D) means at one end of each spoke for tightening the same so that the ring can be accurately centered in relation to the axis of the shaft and so that the spokes cooperate in constraining the ring to move radially with the bearing housing relative to the channel, thus permitting a minimum of clearance to be maintained between the ring and the tips of the blades without danger that the blades will strike the ring.

2. Rotary fan arrangement according to claim 1, characterized in that the spokes are thin steel wires, to offer a small resistance to air flow in the intake channel.

3. In apparatus comprising wall means defining a ductlike channel, a bearing housing coaxially fixed in said channel, a shaft coaxially rotatable in the bearing housing, and a fan in the channel having a hub fixed to said shaft and a plurality of blades projecting substantially radially from the hub with their tips equidistant from the axis of the shaft:

(A) a stiff but slightly elastically deformable ring encircling the fan blades and received in a radially inwardly opening circumferential recess in the wall means, the radially inner surface of the ring being substantially flush with the axially adjacent inner surfaces of the wall means and being radially spaced a small distance from the orbit of the blade tips;

(B) an annular sealing strip of resilient material between each end of the ring and its axially adjacent portion of the wall means, said sealing strips cooperating with the radially inner surface of the ring and its axially adjacent inner surfaces of the wall means to provide a substantially smooth, continuous surface extending axially through the neighborhood of the blade tips, and said sealing strips by their resilience permitting radial motion of the ring relative to the wall means;

(C) a plurality of substantially radially extending spokes, each connected at one end to the bearing housing and at its other end to the ring, said spokes being disposed close to the plane of the blades; and

(D) means at one end of each spoke for tightening the same so that the ring can be accurately centered in relation to the axis of the shaft and so that the spokes cooperate in constraining the ring to move 'r'adially with the bearing housing relative to the channel to permit a minimum of clearance to be maintained between the ring and the tips of the blades without danger that the blades will strike the ring.

4. The apparatus of claim 3 further characterized by:

a plurality of resilient supporting elements connected between the ring and said wall means and confined between the radially outer surface of the ring and its opposing surface of the recess References Cited by the Examiner UNITED STATES PATENTS 525,928 9/ 1894 Thompson 230120 1,233,610 7/1917 Schleicher 230120 3,173,605 3/1965 Harris 230120 SAMUEL LEVINE, Primary Examiner.

HENRY F. RADUAZO, Examiner. 

1. IN APPARATUS COMPRISING WALL MEANS DEFINING A DUCTLIKE CHANNEL, A BEARING HOUSING COAXIALLY FIXED IN SAID CHANNEL, A SHAFT COAXIALLY ROTATABLE IN THE BEARING HOUSING, AND AN FAN IN THE CHANNEL HAVING A HUB FIXED TO SAID SHAFT AND A PLURALITY OF BLADES PROJECTING SUBSTANTIALLY RADIALLY FROM THE HUB WITH THEIR TIPS EQUIDISTANT FROM THE AXIS OF THE SHAFT; (A) A STIFF BUT SLIGHTLY RESILIENT RING ENCIRCLING THE FAN BLADES WITH A SMALL CLEARANCE BETWEEN THE TIPS OF THE BLADES AND THE RING; (B) MEANS SUPPORTING THE RING ON SAID WALL MEANS, AT THE RADIALLY INNER SURFACE THEREOF, SAID MEANS PROVIDING FOR RADIAL MOTION OF THE RING RELATIVE TO THE WALL MEANS AND PROVIDING A SEAL BETWEEN THE RING AND THE WALL MEANS; (C) A PLURALITY OF SUBSTANTIALLY RADIALLY EXTENDING SPOKES, EACH HAVING ITS OPPOSITE ENDS CONNECTED RESPECTIVELY TO THE BEARING HOUSING AND TO THE RING, SAID SPOKES BEING DISPOSED CLOSE TO THE PLANE OF THE BLADES; AND (D) MEANS AT ONE END OF EACH SPOKE FOR TIGHTENING THE SAME SO THAT THE RING CAN BE ACCURATELY CENTERED IN RELATION TO THE AXIS OF THE SHAFT AND SO THAT THE SPOKES COOPERATE IN CONSTRAINING THE RING TO MOVE RADIALLY WITH THE BEARING HOUSING RELATIVE TO THE CHANNEL, THUS PERMITTING A MIMIMUM OF CLEARANCE TO BE MAINTAINED BETWEEN THE RING AND THE TIPS OF THE BLADES WITHOUT DANGER THAT THE BLADES WILL STRIKE THE RING. 